Brass plated rubber adherent steel wire



Jan. 27, 1959 o. E. ADLER l 2,870,526

BRAss PLATED RUBBER ADEERENT STEEL WIRE Filed sept. 23, 1955 FIEE ofwel@ina/er 5y-n y United States Patent O BRASS PLATED RUBBER ADHERENT STEELWIRE Orville E. Adler, Niles, Mich., assignor, by mesne assignments, toNational-Standard Company, a corporation `of Delaware ApplicationSeptember 23, 1955, Serial No. 536,075 4 claims. (ci. zei- 1835) Thisinvention relates to a rubber coated steel wire, and in particular itrelates to a steel wire which-is rst plated with zinc and then withbrass to provide a good base for rubber adhesion and also to lengthenthe storage life of the wire prior to rubber coating.

Steel wire'which is to be coated with rubber, as is copper which isapplied over the zinc must normally be i quite thin. The copper itselfdoes not provide a satisfactory base for rubber adhesion; but migrationbetween the Zinc and the copper produces a brass coating which providesvery satisfactory rubber adhesion. This type of wire and the method ofmaking it are disclosed in Domm Patent 2,002,261.

Wire of the type disclosed in the Domm patent is completely satisfactoryexcept that the migration causes a storage problem for the followingreasons:

Various rubber mixes require somewhat different brass alloys for bestrubber adhesion, with a range between 60% and 80% copper, balance zinc.The optimum for most purposes is 70% copper or 0.425 part zinc to onepart copper. The minimum thickness of zinc which is needed for adequatecorrosion resistance is about 00004. On the other hand, the thickness ofcopper which may be used to permit migration of zinc through the copperto produce a thoroughly rubber-adhesive brass alloy at the surfacewithin any ordinary storage time from plating to use ordinarily must befrom 000004" to 000010". Migration continues steadily until thecopper-Zinc alloy reaches equilibrium for the amounts of the two metalswhich were originally put on the wire. This means that the copper onzinc wire must be used within a certain length of time or the percentageof zinc at the outer surface will become too high for good rubberadhesion. This may best be shown by converting the thickness figuresinto equivalent weights of zinc and copper per kilogram of wire. So, forexample, on a .037" steel wire the minimum zinc is 4 grams per kilogramof wire, While the copper ranges from .5 to 1.3 grams per kilogram. Thismeans that even with the minimum zinc coating there are from 3 to 8parts zinc to 1 part copper; so that with excessive storage the wire cango far past the desired copper-zinc ratio for good rubber adhesion. Theproblem can not be met by using a thick copper coating, because then ifthe storage time is short the wire surface contains too little zinc foradequate rubber adhesion.

Most conditions of storage and use can be met by providing a wire havinga copper coating in the range previously specified. However, it does notsatisfy some situations such as export shipment, especially into thetropics,

where there is a long storage period before the wire is used for rubberadhesion and where the wire is exposed to severely corrosive conditions.Wide variations in the time before wire may be used and in the storageconditions to which it may be subjected make it impractical to use thecopper on zinc wire. To assure that the wire will not pass the zone ofoptimum rubber adhesion the copper coating should be thick; but toassure that it will reach that zone by the time it is to be used thecoating must be relatively thin. The problem is one of increasingstorage life while retaining adherence characteristics.

lt has been supposedthat brass plate on zinc would offer no solution tothe problem of increasing storage life while retaining adherencecharacteristics, because with two plates of equal thicknes surfacedeterioration through rubber-adherent brass occurs about twice as fastas through copper. This is logical, since the rubber-adherent brass isfrom 20% to 40%v zinc to begin with, so it must Start away from itsoptimum percentage of zinc as soonas it is plated, while with copperplate the zinc migration carries it toward the optimum range for sometime before it starts to deteriorate from excessive zinc.`

lt has now been Adiscovered that in spiteof the more rapid surfacedeterioration of brass due to zinc migration, a wire which has over thezinc a brass plate in the range for optimum rubber adherence whenfabricated is far more satisfactory for long and severe storage than isa wire having only copper on the Zinc. While the wire may be usedimmediately, because it is fabricated with a rubber adherent brass alloycoating, it may also be provided with a brass coating of sufficientthickness to carry it through any storage time or conditions which maybe encountered, without reducing its rubber adhesion. Thus, contrary toa copper on zinc wire, there is no apparent upper limit to the thicknessof brass which may be used and still have satisfactory rubber adherencewhen used. So, for example, where the range of copper thickness is from000004 to 000010" for a satisfactory commercial product, a brass plateof 000017 (2 grams per kilogram) may be used.

The invention is illustrated diagrammatically in the drawing wherein:

Fig. l shows a broken view of a wire cut away to show the variouscoatings; and

Fig. 2 is an end view of the same.

lt is to be understood that the distinct layers of zinc and brass areshown only for purposes of illustration, and that the drawing isnecessarily very much out of scale.

An example of the process of the invention will be given in connectionwith steel tire bead reinforcing wires having a diameter of .037 inch.It will be understood that to maintain the same thickness of zinc and ofbrass on a heavier wire the weight of zinc and of brass per kilogram ofsteel must be reduced. The wire has a typical composition as follows:

Percent Carbon .65 Manganese .80 Phosphorous .015 Sulphur .025 Silicon.095

Balance is iron with traces of impurities.

40 grams per liter of zinc and O gram per liter of free cyanide with apH of 10.6.

The brass plating bath is maintained at a temperature of 150 F. and acurrent density of 100 amperes per square foot, and with a brass platingtank which is l2 feet long the zinc plated ,Wire is passed through thebath at a speed of 45 feet per minute. Under these conditions a brassplate is deposited on the wire which contains approximately 70% copperand 30% zinc, and has a brass plating weight of 2 grams per kilogram ofwire, which on the .037 wire is .000017" thick.

After leaving the brass plating bath the wires are water washed and airdried in the usual manner.

The resulting brass plated-zinc coated steel Wire may be stored for agreat many months, and may be shipped and stored under severe conditionsof heat and corrosion while still retaining substantially its originaleffec- 4 layer immediately after deposition having a uniform ratio ofcopper to zinc throughout, and having a high degree of stability tochange in its rubber adherence under adverse climatic conditions.

2. The article of claim 1 in which the brass layer is an alloycontaining from 60% to 80% copper, balance zinc.

3. The article of claim 1 in which the brass layer is an alloycontaining 70% copper, balance zinc.

4. The method of producing a rubber-adherent ferrous base wire in whichthe base wire is passed continuously through a molten zinc bath to giveit a zinc coating which is at least .00004 inch thick, and the zinccoated wire is then electroplated with a brass alloy'containing from 60%to 80% copper and the balance zinc, to give said zinc coated wirea'uniforrn outerl layer of brass which is at least .000017 inch thick.

`References Cited in the le of this patent UNITED STATESV PATENTS HarrisMay 22,

1. A FERROUS BASE ARTICLE HAVING A LAYER OF ZINC THEREON WHICH IS ATLEAST .00004 INCH THICK; AND AN ELECTRODEPOSITED AS SUCH LAYER OF HIGHLYRUBBER ADHERENT BRASS ON THE ZINC WHICH IS AT LEAST .000017 INCH THICK,SAID BRASS LAYER IMMEDIATELY AFTER DEPOSITION HAVING A UNIFORM RATIO OFCOPPER TO ZINC THROUGHOUT, AND HAVING A HIGH DEGREE OF STABILITY TOCHANGE IN ITS RUBBER ADHERENCE UNDER ADVERSE CLIMATIC CONDITIONS.